1. Field of the Invention
The present invention relates generally to an improved device for repairing broken anchoring members, and more specifically relates to an improved coupling for repairing broken anchor bolts for holding stationary machinery in place.
2. Description of the Related Art
It is common in the industry to anchor stationary machinery such as pumps, compressors, reciprocating engines, and the like to a foundation using anchoring bolts. Typically, the bolts or studs are set in the foundation and have threaded portions that extend above the foundation to facilitate anchoring of the stationary machinery thereto. However, as those skilled in the art will appreciate, a threaded anchor bolt is a complex piece of machinery in its own right and is subject to a number of complex failure modes.
Bolted fasteners, such as threaded anchor bolts, are prone to failure from overtorquing, undertorquing, fatigue loading, impact loading, ductile overloading, corrosion, metallurgical abnormalities, and loss of preload, to name just a few. Thus, it is often necessary to repair anchor bolts that have failed in service.
Several methods and devices have been developed for repairing broken anchor bolts. Among the prior art solutions, welding has been the least successful. Typically, to weld repair an anchor member, the foundation must first be chipped away from the area adjacent the fracture surface of the anchor member. The fracture surface is then usually ground flat or completely removed by saw cutting. Next, a new section of anchor member, e.g., threaded stud, is welded to the still-embedded failed anchor member. Weld repairing of failed anchor members has been successful in those few cases where the anchor member material is readily weldable, and where the strength requirements of the anchor member are minimal. Weld repairing will typically not be successful on high strength anchor members such as those fabricated from the low alloy 4100 and 4300 series steels, or from high alloy steels. Also, as will be recognized by those skilled in the art, welding produces many microvoids that can serve as fracture initiation sites and lead to the premature failure of the repaired anchor member.
Another prior art method of repairing failed anchor members is that of field threading. To repair a failed anchor member by field threading, the foundation surrounding the failed member must be chipped away to allow a sufficient work space in which to cut threads on the failed member. Typically the chipped out hole should be at least ten to twelve times the anchor member diameter in depth. The fractured anchor member is then cut off two to three inches above the bottom of the chipped out hole. A thread cutting die or similar tool is then used to cut threads onto the failed anchor member. Once the threads have been cut on the fractured anchor member, a coupling nut can be threaded onto the member. Thereafter, a new section of anchor member is screwed into the top of the coupling and extends above the foundation base. After aligning the new section of anchoring member, the chipped out hole is typically filled with epoxy or other suitable grout. The prior art practice of field thread repairing a failed anchor member is time consuming, difficult and prone to failure. Thus, there is a need in the industry, appreciated by those skilled in the art, for a new way of repairing broken anchor bolt members.
The present invention is directed to providing an improved device for repairing broken anchor members which does not require the time consuming, difficult and failure prone practices of weld repairing or field thread repairing. Accordingly, the present invention provides a new anchor bolt repair coupling that overcomes the deficiencies of the prior art.